How to resolve circular dependencies?

[jeron-diovis]

I have a situation almost like here: to send request I need data from some stream, and that stream should be updated when request is completed. I.e., it's a circular dependency.

In RxJS this problem is recommended to solve either with intermediate Subject or with expand operator (which I don't understand for now – looks just like flatMap, what's the difference?)

Kefir does not have subjects, but it has pool. Pool does the trick, but in general this solution looks just like this: pool is subscribed to itself. The problem is that such pool after activation always remains active:

Doc says that pool never ends, but there is nothing about "never deactivates".
To deactivate such pool I should either terminate it at all, or unplug it from itself.

Both cases mean writing some code specially for this purpose – I can't just forget about this pool relying on deactivation of it's single consumer, defined somewhere far far away.

Let say I can't or don't want to write this special code.

So my questions are:

1. Is it ok in general that pool isn't deactivated in described situation? Active stream with no subscriptions looks strange.

2. Is there some "official" way of resolving circular dependencies in Kefir?
   Should I really use pool and explicitly terminate / unplug it?
   Or should I install kefir-bus package and implement Subject-like solution? Like this:

const inputBus = KefirBus()
const request$ = inputBus
  .sampledBy(...some signal...)
  .flatMap(...api call...)
  // just "tap into stream", not `observe`, 
  // to don't cause activation before it's really needed
  .map(x => {
    inputBus.value(...)
    return x
  })

Or smth else?

[mAAdhaTTah]

Is it ok in general that pool isn't deactivated in described situation? Active stream with no subscriptions looks strange.

It might be OK if the resources that are left open as a result of the stream never getting deactivated don't cause a memory leak. That said, I feel like this is a bug, so I'll take a look at that.

Is there some "official" way of resolving circular dependencies in Kefir?

Not really; I'm currently using pool the way you do but experience some glitchy behavior that I think is unavoidable given Observable's sync nature, so my plan is to refactor the circular dependency to manage it a bit more manually. Using KefirBus may be another way of handling it, but it kind of depends on the desired behavior of the circular stream.